Solenoid valve

ABSTRACT

A solenoid valve for controlling a fluid has a first housing part ( 2 ), an axial guide ( 3 ), facing inwards, for an armature ( 4 ) which can be displaced in the axial guide ( 3 ) under the effect of a solenoid ( 5 ) that at least partially surrounds the exterior of the first housing part ( 2 ), a return spring ( 6 ) and a closing element ( 27 ) impacting a valve closing element ( 7 ), and a second housing part ( 9 ) which is arranged coaxially to the first housing part ( 2 ). The solenoid valve according to the invention is characterized in that the first housing part ( 2 ) has a reduced wall portion ( 17 ) which faces inwards towards the armature ( 4 ) and the second housing part ( 9 ) and which effects a magnetic separation of the two housing parts ( 2, 9 ) to at least some extent.

The invention relates to a solenoid valve for controlling a fluid having a first housing part, with an axial guide which is oriented toward the interior for an armature which, under the action of a solenoid that at least partially surrounds the first housing part to the outside, can be moved in the axial guide, with a reset spring and a closing element which acts on the valve closing member, and having a second housing part which is located coaxially to the first housing part.

DE-U-85 22 724 describes a solenoid valve with a first cylindrical housing part formed from a ferromagnetic material and a second, sleeve-shaped housing part which likewise consists of a ferromagnetic material for accommodating a magnet armature which controls a valve seat body of the valve. For this purpose, the valve seat body has several hydraulic medium ports which, in the base position of the solenoid valve, are hydraulically separated from one another by a plunger which is attached to the magnet armature. The two housing parts themselves are magnetically separated from one another, but are physically connected by a ring-shaped, further housing part made of a nonmagnetic material in this respect. The indicated magnetic separation by way of the further housing part serves among other things to oppose a so-called magnetic short circuit in any case and to ensure effective feed of the magnetic lines of force into the magnetic armature if the actuating coil of the known solution is energized.

Due to the further housing part consisting of a nonmagnetic material, the known solution is, however, relatively expensive to implement for magnetic separation and it has been shown that, especially when the known solenoid valve is used at high pressures, a failure site is formed by the other ring-shaped housing part for the magnetic separation.

In order to correct these disadvantages, DE 100 38 139 B4 has already proposed in a guide element of a magnetizable base material and at least one region of reduced magnetizability that the region of reduced magnetizability be implemented as a kind of integral component of the base material. In one configuration of the known teaching, a circumferential groove is made in a pressure pipe suitable for solenoid valves and is provided with an additive material of reduced magnetizability by means of a laser application method or laser welding method, where austenitic materials are indicated as especially suitable, such as in particular nickel, chromium, and manganese, but these laser treatment methods are also associated with a certain cost.

EP 0 951 412 B2 discloses a generic solenoid valve for the actuation of liquid and gaseous working media, this solenoid valve being usable especially for hydraulic brake systems for motor vehicles. The known solenoid valve has a first, preferably cylindrical housing part which is surrounded by a solenoid and which forms a receiver for an armature. The receiver forms an axial guide for the indicated armature, and an energy storage mechanism in the form of a reset spring acts on the armature together with a valve stem which acts on it and which, designed as a kind of valve closing member, for a closing solenoid valve presses on a valve seat that interacts with corresponding fluid ports within the valve body. Coaxially to the first housing part, there is a second housing part which has a cylindrical recess that runs in the longitudinal extension of the solenoid valve and that is connected to the indicated valve ports and is located in the valve seat.

The first and the second housing part are produced in one piece from a ferromagnetic material which surrounds the armature in the form of a thin-walled sleeve which serves as a pole tube and whose wall thickness, which remains the same over its length for reducing a magnetic short circuit, should be no greater than is necessary for reliable accommodation of the mechanical stress. The integral execution of the first with the second housing part, which is necessary in this respect, is done preferably via metal cutting steps and can presuppose correspondingly high production and mounting accuracies.

Based on the aforementioned prior art, the object of the invention is to make available to the experts in the field a solenoid valve which is simple to produce and mount and which moreover ensures reliable, effective magnetic separation to prevent short circuits. This object is achieved by a solenoid valve having the features specified in claim 1 in its entirety.

According to the characterizing part of claim 1, the first housing part is provided with a wall reduction which is oriented toward the interior in the direction of the armature and of the second housing part and which at least partially effects a magnetic separation of the two housing parts from one another. The indicated wall reduction can be easily obtained using production technology, for example, using a rolling treatment tool or pressing tool, and in particular the solution according to the invention does not require the introduction of additive materials in order to help prevent a magnetic short circuit and to be able to effect magnetic separation in order to increase the efficiency of the magnetic system. As a result of the depression which is made from the interior and which forms the wall reduction of the first housing part, the material of the wall of the housing is compressed in this respect so that even at higher compressive stresses, reliable steadying by the indicated wall compression is achieved. Alternatively, the depression can also be made by cutting so that there is no compression of the material in this region. If, for the purposes of this invention, therefore reference is made to a wall reduction, this expresses the fact that viewed geometrically, there is a recess on the inside of the wall of the housing part; but no weakening of the material in terms of a lack of compressive stiffness need be assumed. For one with average skill in the art in the field of solenoid valve technology, it is surprising that he achieves reliable magnetic separation with a wall reduction and still produces effective compressive steadying by the compression of the remaining wall thickness material so that even in the event of failure of the solenoid valve, high pressures can still be reliably accommodated by parts of the magnetic housing relative to the fluid flow or flow of media.

The first housing part is preferably formed in the manner of a thin-walled sleeve as a pole tube in the region of the axial guide for the (magnet) armature, with the sleeve moreover projecting into or beyond the second housing part. Because the first housing part in the overlapping region with the second housing part is constituted as a thin-walled sleeve, the first housing part can be fixed on the second housing part by a forming process, such as, for example, by flanging, without the already mentioned compressive stiffness of the overall device being adversely affected in the process.

Advantageously, it is provided that there be a groove around the outer circumference on the second housing part and that the edge of the first housing part be crimped into it. In addition to a compressively very strong connection of the first housing part to the second housing part, a sealing contact connection is also created in this way.

An especially reliable arrangement for the solenoid valve according to the invention is achieved if the indicated wall reduction is provided in an overlapping region of the armature with the second housing part, in which a ring-shaped end of the armature overlaps a step-shaped shoulder on a side of the second housing part that is adjacent to the armature, where especially preferably, in a position spaced away from the armature to the housing part, a middle section of the groove in the sleeve overlaps an empty space in the overlapping region so that in this way, in addition to a magnetic decoupling, a reliable, power-guiding introduction of the magnetic lines of force into the armature can take place with the valve actuating part.

The individual components of the solenoid valve can also be more easily mounted owing to the simplified handling of two housing parts which are kept shorter in their axial length.

In one structurally advantageous version of the solenoid valve, in the region where the groove is located, the armature is formed as s cylinder which in a traveling motion partially crosses the second housing part which is formed as a piston in this region, and thus, regardless of its position, is continuously in centered engagement with the first housing part.

One option of manually opening the solenoid valve in a kind of emergency operation for a malfunction, for example, dictated by a failure of the solenoid, is enabled by a rod-like stem being supported in the second housing part to be axially displaceable and it being able to be actuated from the outside by means of a set screw which is guided to be able to turn in the second housing part. The extension itself is provided with a radial widening on its one free end and in this way is secured to be axially immovable in the indicated set screw. However, when the set screw or actuating screw is turned by hand, the stem can move the armature, and in this respect the tip, which is connected to the armature as a closing element, is lifted by the valve closing member. The closing element with its tip is inserted into the armature on its free end side and is held by means of a steel ring and a flange. Even for a tight armature, releasing the valve closing member is thus easily possible as soon as the rod-shaped stem with its widened end takes hold of the armature after an idle stroke. In the armature, the closing element itself can have a certain radial play so that even in the event that there are production-dictated alignment errors, the cone of the closing element with its free tip strikes the pilot seat on the valve closing member in the middle without difficulty.

In the valve member, a kind of nonreturn valve is preferably installed which, together with the tip of the closing element, clears or closes a bypass bore in the valve closing member. The reset spring or another type of energy storage mechanism is preferably to be located in a recess in the armature around the stem. The assignment of the valve ports and the shape of the valve closing member can be configured such that flow through the solenoid valve in both directions is possible. The reset spring can be supported on the armature and the second housing part preferably to bring about a closed position of the valve closing member.

The invention is detailed below using one exemplary embodiment which is shown in the drawing. The single figure shows a schematic longitudinal section through the solenoid valve according to the invention, not to scale.

The figure shows in a longitudinal section a solenoid valve 1 for controlling a fluid, such as a liquid working medium for a hydraulic consumer of a hydraulic system, which consumer is not detailed. The solenoid valve 1 is made as a piloted valve which can be activated electromagnetically. In its essential parts, the solenoid valve 1 consists of a cylindrical first housing part 2 with dimensions that change incrementally along its outer and inner diameter.

With its connecting branch 32, which is shown on the right edge in FIG. 1 with an O-ring 34 which has been inserted into a circumferential groove 33, the first housing part 2, forms a fluidic connection to a hydraulic system, not shown, especially to a hydraulic consumer. The connecting branch 32 is part of a valve body 35 in whose axial region the first housing part 2 has a large wall thickness compared to its other wall regions. In this respect, the connecting branch 32 forms a type of cartridge valve. A valve port 29 which is made radially in the valve body 35 from the two sides can be connected to its valve port 30, which is routed centrally and axially out of the connecting branch 32, where a valve closing member 7 made as a valve spool controls this fluid-carrying connection. The valve closing member 7 is made as a stepped spool and is axially actuated by way of a closing element with tip 27. The press fit 24 is created by a sealing means 25 in the manner of an O-ring fitting into corresponding receivers resting on the closing element and on the armature 4. The valve closing member 7, with its right edge shown in FIG. 1, forms a valve seat together with the bore which constitutes the valve port 30.

The conical closing element with its tip 27 rests in a bypass bore 28 in the valve closing member 7 with its right free end. A second bypass bore 28′, which extends through the valve closing member 7 radially with a distance to the bypass bore 28 which projects centrally through the valve closing member 7 and is arranged parallel to the latter, is connected to the valve port 29 to carry fluid via a corresponding throttle site. Likewise, the bypass bore 28 is connected via a throttle site to a rear pressure space 36, where the tip of the closing element in the operating position shown in the figure mates with this throttle site. In this respect therefore, the bypass bore 28′, with the tip 27 of the closing element removed, forms a fluid-carrying connection with respect to the rear pressure space 36, which extends between magnet armature 4 and the facing end side of the valve closing member 7.

A nonreturn valve 26 is located on the end of the valve closing member 7 facing the valve port 30. Viewed in the direction of looking at the figure, on the left the first housing part 2 undergoes transition from the valve body 35 into a thin-walled sleeve 14, which forms the so-called pole tube within the solenoid valve. Furthermore, the sleeve 14 forms an axial guide 3 for the armature 4 over a length which corresponds to about half its total length. A lubricating medium can be placed between the magnet armature 4 and the sleeve 14, or parts of the inner housing wall of the sleeve 14 are widened in their outside diameters relative to the other wall parts somewhat in diameter so that offset lubricating pockets form in which the fluid then forms a kind of sliding seal for the magnet armature 4.

The rod-shaped stem 8 extends through the piston-like armature 4, which can move depending on the energizing of a solenoid 5 surrounding the sleeve 14 in its essential length. The stem 8 is guided with an extension 11 through a recess 10 of a second housing part 9 whose free end region is adjoined by a set screw 23 which is rotationally guided by way of a corresponding inner screw connection in the second housing part 9. When a head 37 with a knurl is turned, the stem 8 can be moved and can clear the valve closing member 7 via the armature 4 and the closing element which has been inserted into the armature 4 with tip 27 in the sense of an opening position. External cover caps can be removed from the other magnet housing parts for the corresponding emergency operation.

Like the first housing part 2, the second housing part 9 is essentially a cylindrical, one-piece body, with corresponding diameter adjustments along its outer side. The second housing part 9 is surrounded by the sleeve 14 of the first housing part 2 to approximately to half of the axial extension, forming a plug connection 12, with the second housing part 9 having a circumferential groove 16 into which an edge 15 of the sleeve 14 is crimped. The forming region 13 of the sleeve 14 in the longitudinal section is constituted as right-angle bend; i.e., after forming, the edge 15 comes to rest offset in parallel in the circumferential groove 16. This molding process can be carried out with a pressing tool or rolling treatment tool. Furthermore, there is an O-ring 38 between the sleeve 14 and the second housing part 9 in a groove of the second housing part 9, and thus it seals the first housing part 2 against the second housing part 9.

For magnetic separation of the two housing parts 2, 9, in the axial middle of the solenoid 5, the sleeve 14 is provided with a wall reduction 17 to approximately half of the other wall thickness of the sleeve 14. The wall reduction 17 is formed by a groove 18 with flanks 20 which extend flat on the inner circumference 19 of the sleeve 14. Furthermore, the wall reduction 17 encompasses the inner region of the sleeve 14 in the manner of a ring. The wall reduction 17 facilitates the magnetic separation, especially between the two housing parts 2, 9, and the armature 4 is located in its forward position shown in the figure, between an annular end 39 of the armature 4 and an adjacent, assigned step-shaped shoulder, on a side of the second housing part 9 adjacent to the armature 4, an empty space is formed which further promotes the magnetic separation on the one hand and on the other hand allows a defined transition of the lines of force from the armature 4 to the housing part 9. Moreover, with this type of production of the magnetic separation of the two housing parts 2, 9 from one another, no thermal loading of the components is necessary at all, such as, for example, in the known hard-facing of a nonmagnetic material, so that, when the components are joined, stresses and material distortion that adversely affect the accuracy cannot occur. The indicated empty space can also be filled with fluid, which can be accordingly displaced again in the travelling motion of the armature 4, for example, via the sliding seal of the armature 4.

There is a small radial play of the armature 4 in the region of the wall reduction 17. In all other respects, the armature 4 with its ring-like ends is guided in the second housing part 9. In this way, in the overlapping region 21 a type of piston-cylinder arrangement is implemented which acts on the armature 4 to center it so that it is always supported in a guided manner on the second housing part 9 at its left and right free ends.

As an energy storage mechanism, a reset spring 6 is placed around the stem 8 in a cylindrical bore of the recess 22 which extends from the end 39 of the armature 4 that faces the second housing part 9. The reset spring 6 is supported on a seal arrangement 40 around the stem extension 11. The seal arrangement 40 is placed around the extension 11 in the manner of a gland packing and seals the stem 8 in turn to prevent loss of a hydraulic medium relative to the second housing part 9. In the intermediate space between the armature 4 and the second housing part 9, hydraulic media can appear which, via a longitudinal bore 42 in the armature, can traverse the latter from its rear end side to the front end side in the direction of the pressure space 36 and vice versa. In this way, there is balancing of the hydraulic medium so that in the region of the armature 4 neither an overpressure nor an underpressure can build up which could otherwise lead to problems in the operation of the armature 4. The solenoid valve 1 furthermore has a shielding housing, especially around its solenoid 5, with appropriate plastic and elastomer material being used here. This magnet structure is conventional for solenoid valves so that it will not be further detailed here. To energize the solenoid 5, a plug 41 is used which is attached to the upper side wall of the valve housing for linking to a control and current supply unit, which is not detailed.

Flow can take place through the valve body 35 of the solenoid valve 1 both from the valve port 29 to the valve port 30 and also vice versa. In the energized state of the solenoid 5, the armature 4 and the closing element with tip 27, as well as the valve closing member 7, viewed in the direction of looking at the figure, are moved to the left against the reset force of the reset spring 6, with flow through the valve body 35 in both directions between the valve ports 29 and 30 then being possible.

In the unenergized state of the solenoid valve, however, flow of the hydraulic medium from the valve port 29 to the valve port 30 is prevented; but conversely there is the possibility that the fluid connection may exist between the valve port 30 and the valve port 29. For this flow direction from port 30 to port 29, however, the valve spool 7 must be pushed against the force of the reset spring 6; this takes place, for example, at a pressure difference of about 1.5 bar (check function). As described, the solenoid 5 is not energized here. With the solution according to the invention, a type of 2/2-way seat valve is therefore implemented which, magnetically actuated and piloted as a cartridge valve, can control pressures of even 350 bar and which is closed in the normal state and which, as shown, allows a return or reverse flow function. 

1. A solenoid valve for controlling a fluid having a first housing part (2), with an axial guide (3) which is oriented toward the interior for an armature (4) which, under the action of a solenoid (5) that at least partially surrounds the first housing part (2) to the outside, can be moved in the axial guide (3), with a reset spring (6) and a closing element (27) which acts on the valve closing member (7), and having a second housing part (9) which is located coaxially to the first housing part (2), characterized in that the first housing part (2) has a wall reduction (17) which is oriented toward the interior in the direction of the armature (4) and of the second housing part (9) and which at least partially effects magnetic separation of the two housing parts (2, 9) from one another.
 2. The solenoid valve according to claim 1, characterized in that the first housing part (2) has a thin-walled sleeve (14) as a pole tube which essentially forms the axial guide (3) for the armature (4), and that the second housing part (9) projects into the sleeve (14) at least partially in contact with the sleeve (14).
 3. The solenoid valve according to claim 2, characterized in that the sleeve (14) has the wall reduction (17) in the form of a groove (18) on its inner circumference (19).
 4. The solenoid valve according to claim 3, characterized in that the groove (18) has flat flanks (10) which extend to the adjacent wall regions of the sleeve (14).
 5. The solenoid valve according to claim 1, characterized in that the wall reduction (17) is located in an overlapping region (21) of the armature (4) with the second housing part (9), in which a ring-shaped end (39) of the armature (4) overlaps a step-shaped shoulder on a side of the second housing part (9) that is adjacent to the armature (4).
 6. The solenoid valve according to claim 5, characterized in that in a position spaced away from the armature (4) to the housing part (9), a middle section of the groove (18) in the sleeve (14) overlaps an empty space in the overlapping region (21).
 7. The solenoid valve according to claim 1, characterized in that the first housing part (2) and the second housing part (9) are connected to one another as a plug connection, in which the first housing part (2) at least partially overlaps the second housing part (9) viewed in the axial direction of actuation of the valve, and that one free end of the housing part (2) made as a flanged edge mates with a circumferential groove (16) in the second housing part (9).
 8. The solenoid valve according to claim 7, characterized in that the other free end of the first housing part (2) forms a valve body (35) for the valve closing member (7), which valve closing member, to the extent that it is concomitantly controlled by the closing element (27), clears or blocks a fluid-carrying connection between two valve ports (29, 30) of the valve body (35).
 9. The solenoid valve according to claim 1, characterized in that the second housing part (9) has a set screw (23) that is dynamically connected to a stem (8), and, when the set screw is manually actuated, the stem (8), which with an extension (11) at least partially extends through the second housing part (9) along an axially routed recess (10), can be moved together with the armature (4) into a position in the sense of an opening of the valve closing member (7).
 10. The solenoid valve according to claim 1, characterized in that the solenoid valve (1) is piloted. 